| Month | High | Low | Rain | Wet days | Score |
|---|---|---|---|---|---|
| January | 8.3° | 3.9° | 117.6mm | 22.4 | 33 |
| February | 8.6° | 3.9° | 106.1mm | 20.5 | 34 |
| March | 9.5° | 4.5° | 77.6mm | 19.2 | 36 |
| April | 11.3° | 6° | 58.2mm | 15.8 | 42 |
| May | 13.5° | 8° | 68.2mm | 17 | 49 |
| June | 15.4° | 10.4° | 72.5mm | 16.9 | 55 |
| July | 16.9° | 12.2° | 90.3mm | 19.1 | 60 |
| August | 17.2° | 12.6° | 100.6mm | 19.8 | 61 |
| September | 16.1° | 11.3° | 91.7mm | 19.2 | 58 |
| October | 13.6° | 8.9° | 120.6mm | 22.1 | 50 |
| November | 10.8° | 6.4° | 116.5mm | 22.9 | 41 |
| December | 9.1° | 4.6° | 135.4mm | 23.4 | 35 |
January in Londonderry County Borough averages a daily high of 8.3°C with nights around 3.9°C. Expect roughly 22.4 wet days totalling 117.6mm. A hard month to visit for comfort alone.
February in Londonderry County Borough averages a daily high of 8.6°C with nights around 3.9°C. Expect roughly 20.5 wet days totalling 106.1mm. A hard month to visit for comfort alone.
March in Londonderry County Borough averages a daily high of 9.5°C with nights around 4.5°C. Expect roughly 19.2 wet days totalling 77.6mm. Demanding conditions — pack for it and plan indoor options.
April in Londonderry County Borough averages a daily high of 11.3°C with nights around 6°C. Expect roughly 15.8 wet days totalling 58.2mm. Demanding conditions — pack for it and plan indoor options.
May in Londonderry County Borough averages a daily high of 13.5°C with nights around 8°C. Expect roughly 17 wet days totalling 68.2mm. Demanding conditions — pack for it and plan indoor options.
June in Londonderry County Borough averages a daily high of 15.4°C with nights around 10.4°C. Expect roughly 16.9 wet days totalling 72.5mm. Generally workable, with some weather to plan around.
July in Londonderry County Borough averages a daily high of 16.9°C with nights around 12.2°C. Expect roughly 19.1 wet days totalling 90.3mm. Generally workable, with some weather to plan around.
August in Londonderry County Borough averages a daily high of 17.2°C with nights around 12.6°C. Expect roughly 19.8 wet days totalling 100.6mm. Generally workable, with some weather to plan around.
September in Londonderry County Borough averages a daily high of 16.1°C with nights around 11.3°C. Expect roughly 19.2 wet days totalling 91.7mm. Generally workable, with some weather to plan around.
October in Londonderry County Borough averages a daily high of 13.6°C with nights around 8.9°C. Expect roughly 22.1 wet days totalling 120.6mm. Demanding conditions — pack for it and plan indoor options.
November in Londonderry County Borough averages a daily high of 10.8°C with nights around 6.4°C. Expect roughly 22.9 wet days totalling 116.5mm. Demanding conditions — pack for it and plan indoor options.
December in Londonderry County Borough averages a daily high of 9.1°C with nights around 4.6°C. Expect roughly 23.4 wet days totalling 135.4mm. Demanding conditions — pack for it and plan indoor options.
Each month scores out of 100. It starts at 100 and loses points for daytime highs outside a 20–27°C band, for wet days, and for nights below 2°C. Nothing else is weighted in — no crowd data, no prices, no opinion. Londonderry County Borough peaks at 61.
Based on 30 years of records, June–September scores highest for comfort in Londonderry County Borough, balancing daytime temperature against rainfall.
August is the warmest, averaging a daily high of 17.2°C.
December is the wettest, averaging 135.4mm of rain across roughly 23.4 wet days.
January is the coolest month, with average daily highs around 8.3°C.